The invention relates to a device for transporting yarn, said device comprising a central mast, which is equipped with a plurality of circulating transport belts arranged in a polygonal pattern when viewed in cross section. At least one yarn is wound around the central mast and the transport belts in controlled loops by means of a winding flyer. The central mast is supported in a mounting on its end towards the winding flyer and in the area of its other end it is provided with supported rollers, which are supported by a supporting roller which is located outside the loops. The supporting roller is connected to a roller drive and the circumferential speeds of the supported rollers are synchronized with the circumferential speed of the supporting roller in preferred embodiments of the invention.
In the case of a device of the general type with which this invention is concerned (European patent 47 468), the central mast is equipped with two lateral friction wheels which are driven by a driven supporting roller. The friction wheels, which function as supported rollers, are tightly connected equiaxially with guiding rollers for the transport belts, so that the latter are also driven. Each transport belt is wound around the relevant guiding roller at an angle of 270.degree., the transport belt being then driven by the supporting roller over the frictional wheel and the guiding roller. The loops of the yarn are nipped between the supporting roller and the friction wheels serving as supported rollers. As the diameter of the guiding rollers is somewhat smaller than the diameter of the friction wheels, there exists a relative speed between the supporting roller and the yarn loops transported on the transport belt. Because of the drive of the friction wheels, a minimum driving force is necessary, which in certain circumstances must be stronger than the proportionate load caused by the central mast, which has to be supported.
It is an object of the invention to provide, in the case of a device of the type mentioned above, for a more careful handling of the loops of the yarns.
This object is achieved according to preferred embodiments of the invention in that the transport belts are driven by their own belt drive, to which belt speed the circumferential speeds of the supporting roller and the supported rollers are synchronized.
The yarns are more carefully handled during transport due to the fact that the belt drive and the roller drive are adapted to each other to such a degree that no relative speed exists between the loops on the one hand and the supporting roller and the supported rollers on the other. As the drive of the transport belts is not affected by a frictional wheel which presses the loops, the pressure of the supported rollers on the supporting roller can be kept lower and need only be so great that the proportionate weight of the central mast is taken up.
For this purpose the roller drive in especially preferred embodiments of the invention comprises a regulatory, infinitely variable gear. This enables an exact synchronization of the circumferential speeds of the supported rollers and the supporting roller with the belt speed.
It is advantageous according to certain preferred embodiments of the invention to allocate guiding rollers for the transport belts to the supported rollers. The loops of the yarns can then be very precisely laterally guided in the area of the nipping line between the supported rollers and the supporting roller.
The guiding rollers can be constructed in different ways. In one development of the invention it is intended that the supported rollers are at the same time the guiding rollers. Thus an exact synchronization between supported rollers and guiding rollers is guaranteed from the start.
In another development of the invention, the guiding rollers are supported independently of the supported rollers and are freely rotatable. This has the advantage that the supporting of the central mast and the guiding of the transport belts become separate functions.
It is advantageous according to certain preferred embodiments that the guiding rollers are adjustable relative to the supporting roller, so that the guiding rollers fit exactly to the nipping line between the supported rollers and the supporting roller.
According to certain preferred embodiments of the invention, the supported rollers are integral with the guiding rollers as well as coaxially arranged with respect to them and preferably slightly conically shaped on their supported surfaces. This is less recommendable for highly sensitive yarns however, as conical friction surfaces result in different circumferential speeds. In the case of lighter bearing pressures, however, this solution is a very practicable, in particular when the slightly conical supported surfaces are somewhat convex.
In a further development of the invention the supporting roller and/or the supported rollers are provided with an elastic coating. This has the advantage firstly that the loops of the yarns are less crushed when passing the nipping line. An additional advantage is a certain coupling by friction which arises, when required, between the supporting roller and the supported rollers, whereby a synchronization with respect to the circumferential speeds is attained. This friction can of course be less than when the drive of the transport belts has also to be effected by this friction, as is the case with prior art arrangements.
The supported rollers have for the purpose of the invention a supported width which is many times that of the transport belts. The pressing of the loops of the yarns is hereby reduced. To simplify the supporting device, it can be provided that a common axle is allocated to the two supported rollers according to certain preferred embodiments.
It is particularly advantageous when the supporting roller has a larger diameter in the area of the supported rollers. This means that the diameter of the supporting roller is smaller outside of the area of the supported rollers, so that outside of the actual nipping line of the loops, impairment of the loops is reduced. For this purpose the supporting roller for each supported roller has two supporting surfaces, so that a defined two-point support arises.
In a particularly advantageous development of the invention the supporting roller is provided with longitudinal grooves. The loops of the yarns are thus crushed only for a very short time during the run through the nipping line, so that impairment remains at acceptable levels. When the longitudinal grooves of the two supporting surfaces are thereby set at least a half a groove width out of line with respect to each other in a circumferential direction of the supporting roller, it is thus ensured that on one of the two supporting surfaces, the central mast is always actually supported without pinching of the yarn.
It can be further provided according to preferred embodiments that yarn guiding elements are allocated to the supported rollers and/or the guiding rollers. These serve the purpose of bridging any discontinuity spots in the area of the supported rollers or guiding rollers and thus contribute further to the careful treatment of the yarns.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.